The objectives of this research are to: (1) obtain more complete definition of the mechanism by which silicate cement protects teeth against caries; and (2) use these data to explore the potential of incorporating the "silicate mechanism" in other materials to provide anticariogenic properties. All the evidence indicates that the caries inhibiting ability of silicate cement is derived from fluoride incorporated during its manufacture. Research indicates that the fluoride, which slowly leaches from the material, acts upon both the hard tooth structure and the plaque. This study is concerned with obtaining more definitive information with respect to the effect on the tooth. It has been shown that the fluoride content of enamel is increased and its acid solubility reduced by direct contact with silicate cement. However, not only does less marginal caries occur in teeth restored with silicate than with other materials, but a lower caries incidence in other regions of the tooth and also in contact areas of adjacent teeth has been reported. This then implies more than a localized effect. Thus, this research proposes first to determine the effect of silicate restorations on the fluoride distribution in the enamel of the restored teeth. The restorations will be placed in extracted molar teeth. After periods ranging from 1 month to 1 year, the fluoride content of enamel biopsies taken from sites adjacent to the restorations and at other sites at prescribed distances from the restoration will be determined. Control data will be obtained from comparable tests using a fluoride-free silicate and also by biopsy of unrestored teeth. Using this same procedure, and the data obtained for silicate cement as a model, the potential anticariogenic properties of other materials which contain fluoride or to which fluoride has been added will be evaluated. These materials include silicophosphate cement, glass ionomer cement, acrylic and BIS GMA resins.